Move
on over, hot peppers. The Mexican state of Tabasco now shares its fame with
corn. That's where an interdisciplinary team of scientists unearthed the latest
evidence for early, domesticated Mexican maize.

The discovery of maize pollen in southeastern Mexico by Kevin G. Pope, Mary
E. D. Pohl and colleagues furthers the longtime pursuit for the origin of agricultural
corn. Now, the date for the earliest known appearance of cultivated maize is
at least 5100 calendar years BC, about a thousand years earlier than the estimates
from actual corncob fossils. The new findings, published in the May 18, 2001,
issue of the journal, Science, include the appearance of a manioc pollen
grain and sunflower seeds. These provide more clues on the diets and interactions
of early people in Mesoamerica.

The Pope and Pohl study now adjusts the antiquity of maize
reported earlier by Dolores Piperno at the Smithsonian Tropical Research Institute
and Kent Flannery at University of Michigan, Ann Arbor. They recorded the earliest
instance of domesticated Mexican maize from corncob fossils in dry, elevated
Oaxaca, Mexico. The recent discovery now challenges this date, due to even older
maize pollen from a wetter, more humid environment near the mouth of the Grijalva
River.

The process of coring, with overlays of (clockwise from right) Manihot species
pollen, small Zea species pollen, and Maize pollen.

"This important research provides another much needed data point documenting
the spread of crop plants, particularly maize, across Mexico," Bruce Smith
said about the research led by co-directors Pope, from Geo Eco Arc Research
in Aquasco, Md., and Pohl, from Florida State University. In Mexico, the three
other excavation sites that show major evidence for early, domesticated maize
are all in the highlands, including Oaxaca.

While the notion is popular that the plant was first cultivated in the highlands
and possibly originated there, genetic information points elsewhere: to a subspecies
of teosinte, a wild grass in the west central Mexican state of Guerrero. This
habitat, in the Balsas River Valley, is a median between lowland and highland
zones.

According to Smith, a curator and Program Director at the National Museum of
Natural History, Smithsonian Institution, "The Tabasco research should
add further fuel to the long unfolding debate regarding exactly when maize was
domesticated in the Balsas, and how quickly it spread up into the highland zones,
and down and through lower elevation coastal zones."

Anthony Ranere, an anthropology professor at Temple University said, "Maize
cultivation has a long history in the Pacific lowlands of Central and northern
South America." He continued, "Kevin Pope, Mary Pohl and collaborators
have shown that maize was introduced into the Gulf coastal lowlands quite early
as well."

The non-wild pollen grains identified by the team, which included John G. Jones,
an anthropologist specializing in pollen at Texas A & M University, were
exotic to their research site. This means the people who moved to the environment
already practiced farming, and they had somehow brought cultivated maize with
them.

The pollen evidence also matched the geologic record from about 5000 BC when
there was an environmental change where the Grijalva River met the Gulf. The
river dumped lots of sediment, which expanded the coastline and created brand
new areas for early humans to live.

"What you see with more traditional archaeological techniques is not always
what's there," Pope said. In addition to conventional excavation, his team
used cores, or vertical samples of earth, which allowed them to detect pollen
grains far beneath the surface.

"One really interesting implication of the research is that these early
groups developed a more productive race of maize soon after settling the coastal
lowlands of Tabasco," Ranere said. "And maize was not the only crop
in the mix; they have evidence for domesticated manioc and sunflower pretty
early on as well," he continued.

Two different types of pollen grains were identified at Tabasco, according
to the study. The first, primitive maize, appeared about 100 years before the
second, more developed one. The small maize pollen disappeared from the cores
at about 2500 BC. "We don't know whether the range in size and morphology
represents variability caused by selective pressure or the cultivation of more
than one type of Zea," Pohl said. Zea is the genus name for
maize and corn.

The presence of manioc, a starchy root, in Tabasco lends strong weight to hypotheses
that crops were exchanged between people in Latin America as early as 4600 BC,
when a manioc pollen grain appeared, said Pohl. Manioc is thought to be native
to South America, existing as early as 5800 BC. The same could be said for corn
dispersal southward if manioc had traveled north to Mexico. Early maize discoveries
were also found in Ecuador and Panama. "It was probably mostly diffusion
by exchange from one group to another, but people may also have been moving
long distances in the process of exchange, especially along coastal routes,"
Pohl said.

Piperno said of corn, "Having just that crop in the diets south of Mexico
illustrates very well that you have some sort of agricultural system in place
at that time."

Domesticated sunflower, too, appeared in 2500 BC according to the Pope and
Pohl study, challenging others' data that the domesticated version originated
in the Eastern United States.

Still, it is corn that attracts the most attention. "Maize is the crown
jewel of New World domesticates because it's one of the most important crops
in the world today," Smith said. "If you're talking about corn, everyone
knows corn. It's one of the heavyweights of domesticates."